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Rick
Rick, Factory Authorized Trainer
Category: Small Engine
Satisfied Customers: 8057
Experience:  Outdoor Power Equipment technical trainer since 1990, covering eight states.
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17.5 troybilt engine wont start, backfires once in awhile.

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17.5 troybilt engine won't start, backfires once in awhile. spark to plug, new sparkplug, new gas filter, new gas, clean air filter , turns over fine, just won't start
Was there an impact or a sudden stop before this started happening?
Customer: replied 6 years ago.
The lawnmower ran out of gas, put gas in it but it wont start, so chged plug, gas filter, nothing
Does it try to start if you squirt a tablespoon of gas in the spark plug hole?
Customer: replied 6 years ago.
No, it grinds maybe back fire but does not try to start. I sprayed starting fluid in spark plug hole will not start but plug is usually wet when I remove it again. but it will spark out of the hole.

It sounds like a sheared flywheel key since you're getting spark and it's backfiring. A sheared key would throw it out of time. The other thing I would check for would be a stuck valve. Do you feel compression at the spark plug hole with your thumb when the engine is turning over?

 

 

Customer: replied 6 years ago.
Yes there is compression at the hole with the spark plug out
Then I would check the flywheel key. Odds are that it's sheared.
Customer: replied 6 years ago.
where in the world is the flywheel key

Believe it or not -- in the flywheel. Innocent

 

You remove the flywheel nut and washer to do an inspection. If you can let me know what engine is on there (model, type/spec, code/serial) I should be able to get a drawing to post for you. Here's some good info that may help.

 

http://outdoorpowerinfo.com/repairs/flywheel_removal.asp

 

Rick and other Small Engine Specialists are ready to help you
Customer: replied 6 years ago.
17.5 1/c overhead valve 5BSXS.5012VP 276016

There should be a model, type, and code. Those numbers are for EPA emissions.

 

http://www.jackssmallengines.com/briggs_and_stratton_model_locator.cfm

 

Customer: replied 6 years ago.
13AN779G766
Customer: replied 6 years ago.
I am sorry, I had an emergency.,that is why you didn't here from me. I will pay you for all your trouble but now I have to find it's location. Thanks
Customer: replied 6 years ago.
I am sorry, I had an emergency.,that is why you didn't here from me. I will pay you for all your trouble but now I have to find it's location. Thanks

Understood. Let me know when you would like to continue...

 

Here's a parts list for your engine to show you how everything goes together.

 

http://www.partstree.com/parts/?lc=Briggs+and+Stratton&mn=31C707-0154-E1